JPS62122631A - Tonometer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tonometer used in eye clinics and the like, which utilizes the deformation of the cornea caused by air flow.

[Prior Art] Tonometers that have been commonly used include the so-called N tonometer, which measures intraocular pressure by applying air pressure to the eyeball and applanating the cornea.
CT (Non Contact
r) is well known. As shown in Fig. 2, this tonometer ejects an air flow A from a nozzle 1 to the cornea Ec.
Applanate c. In this process, the cornea Ec is irradiated with parallel light from the light source 2 via the convex lens 3, and the applanation state of the cornea Ec is detected by a light receiving optical system including an objective lens 4 and a photoelectric detector 5. However, this tonometer has the disadvantage of causing discomfort to the subject due to the strong air pressure.

[Object of the Invention] The object of the present invention is to eliminate the above-mentioned drawbacks, to apply a slight deformation to the cornea using weak air pressure, and to determine the amount of deformation by optical means, thereby not causing discomfort to the subject. An object of the present invention is to provide a tonometer that can accurately measure intraocular pressure.

[Summary of the Invention] The gist of the present invention to achieve the above object is to provide a device that deforms the cornea using air pressure and measures intraocular pressure based on the amount of deformation, in which a light beam is projected onto the cornea from a direction oblique to the air flow. Then, through the corneal reflection optical system, an optical position detection element placed at a position conjugate to the cornea detects the displacement of the incident position of the corneal reflection light when airflow is applied, and detects the amount of corneal deformation. This is a tonometer that measures intraocular pressure.

[Embodiment 1 of the invention The present invention will be explained in detail based on illustrated embodiments.

In FIG. 1, E is the eye to be examined, and a nozzle 10 that blows out an air flow A is arranged in front of the eye. and,
A point light source 11 is placed diagonally in front of the eye E to be examined, and a condenser lens 12 is provided between the eye E and the eye E to be examined. Point light source 1
An imaging lens 13 and an optical position detection element 14 are arranged in the direction of the reflected light L2 of the light beam L1 from 1 on the cornea Ec, and this detection element 14 is approximately conjugate with the point light source 11 and the cornea Ec. There is. The position of the cornea Ec on which the light beam L1 from the light source 11 is incident is preferably set at the center of the airflow A, that is, the vertex of the cornea Ec, since this maximizes the amount of displacement to be detected.

The light beam L1 emitted from the light source 11 is focused by the condensing lens 12 onto a point P on the cornea Ec from an oblique direction with respect to the air flow A, and is reflected by the cornea Ec.

The light beam L2 reflected by the cornea Ec enters a point Q on the optical position detection element 14 via the imaging lens 13.

Here, an air flow A is applied to the cornea Ec from the nozzle 10 in the direction of the arrow.
When applied, the cornea Ec deforms as shown by the dotted line,
The reflection point on the cornea EC moves from P to P'. At this time, the light flux on the optical position detection element 14 also moves from Q to Q',
The amount of deformation of the cornea Ec can be determined from the amount of displacement.

The amount of deformation of the cornea Ec is related to the intraocular pressure, and if this relationship is determined in advance, the intraocular pressure can be determined by knowing the amount of deformation. It is preferable that the incident spot of the light beam L1 on the cornea Ec be condensed by the condenser lens 12 to have a small diameter, since this is not affected by the corneal curvature.

In this case, the intraocular pressure may be determined by the air pressure that provides a predetermined amount of corneal deformation while changing the air pressure, or the amount of deformation when a constant pressure is applied may be measured. The optical position detection element 14 may be an array sensor such as a CCD (charge-coupled device), or may be a semiconductor device detection element that outputs an analog quantity.

[Effects of the Invention] As explained above, the tonometer according to the present invention can accurately measure the amount of corneal deformation even when the cornea is deformed by air pressure, which is much weaker than by conventional applanation. This means that intraocular pressure can be measured without causing discomfort to the patient.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of a tonometer according to the present invention, and FIG. 2 is a block diagram of a conventional optical system. 10 is a nozzle, 11 is a point light source, 12 is a condensing lens,
13 is an imaging lens, and 14 is an optical position detection element.

Claims (1)

[Claims] 1. In a device that deforms the cornea using air pressure and measures intraocular pressure based on the amount of deformation, a beam of light is projected onto the cornea from a direction oblique to the air flow, and the reflected light from the cornea is transmitted through an optical system. A tonometer characterized in that an optical position detection element placed at a conjugate position on the cornea detects the displacement of the incident position of corneal reflected light when airflow is applied, thereby detecting the amount of corneal deformation and determining the intraocular pressure. . 2. The tonometer according to claim 1, wherein the intraocular pressure is determined from the amount of corneal deformation when the air pressure is constant. 3. Claim 1, in which the air pressure is variable and the intraocular pressure is determined from the air pressure that provides a constant amount of corneal deformation.
Tonometer as described in Section.